1. Field of the Invention
The present invention generally relates to a process for the preparation of trifluoromethyl iodide. More particularly, the present invention relates to a process for the preparation of trifluoromethyl iodide from CF3—W and Z-I wherein W is CF3, hydrogen or bromine and Z is hydrogen, iodine or chlorine.
2. Description of the Prior Art
An article by Dhooge et al. in Proceedings of the 4th Conference on Aerospace Materials, Processes, and Environmental Technology, page 259–268 (2000), describes vapor phase production process for the preparation of CF3I by the reaction between CHF3 with I2 in the presence of a catalyst including alkali metal salts supported on an activated carbon carrier. The reaction mechanism appears to proceeds via CF2 carbenes formed on the catalyst surface as intermediates, followed by carbene disproportionation to CF3 radicals, followed by reaction with I2 to give CF3I (see Nagasaki, Noritaka et al., Catalysis Today (2004), 88(3–4), 121–126).
JP 52068110 (1977) describes the preparation of CF3I by vapor-phase reaction of Freon 23 with iodine in the presence of alkali or alkaline earth metal salts.
DE 1805457 (1970) describes the preparation of CF3I and C2F5I from the reaction of corresponding bromides and KI without solvent.
Naumann et al., J. Fluorine Chem., 67(1), 91–3(1994) describes the preparation of CF3I from CF3Br by a multi-step reaction, which employs elemental Zn.
European Patent Application EP 266,281 A1 (1988) describes the preparation of CF3I from CF3Br by contact with a metal or an alkali metal dithionite and SO2 followed by treatment with iodine in a carboxylic or sulfonic acid.
Lee, K. -H. et al., Hwahak Konghak, 39(2), 144–149 (2001) describes the preparation of CF3I by iodination of CF3CO2H with iodine using a flow reactor over various salt-impregnated catalysts.
Su, D. et al., J. Chem. Soc., Chem. Commun. (11), 807–8 (1992) describes the preparation of CF3I by treatment of XCF2CO2Me (X═Cl or Br) with iodine in the presence of potassium fluoride and copper (I) iodide.
Chiriac, M. et al., Inst. Tehnol. Izot. Mol., 33(11), 1018–20 (1982) describes the preparation of CF3I from Ag-trifluoroacetate.
However, in view of the high cost of the raw materials required and the formation of solid by-products that are difficult to dispose of because of their adverse impact on the environment, none of these methods provide a practical and economical process which could be adapted to large scale process for the preparation of CF3I.
Furthermore, there is no report in the literature of any catalytic vapor-phase process for making CF3I in high yield. Therefore, a high yield, catalytic vapor-phase process, which avoids the formation of solid by-products and the adverse impact of such solid by-products on the environment would be welcome by the Chemical Industry.
The above described problems can be avoided by the use of a process for the preparation of trifluoromethyl iodide from CF3—W and Z-I wherein W is CF3, hydrogen or bromine and Z is hydrogen, iodine or chlorine according to the present invention.